KR100980022B1 - Driving method of liquid crystal display - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal display, and more particularly, to a method for driving a liquid crystal display that can prevent distortion of a common voltage.

According to one embodiment of the invention, a plurality of pixels arranged in a matrix form, a signal control unit for providing a control signal, a data driver for supplying a data voltage in accordance with the control signal, and a plurality of transfer the data voltage to the pixel And a precharge signal for precharging a predetermined voltage to the pixel, wherein the control signal comprises applying a first precharge voltage to a first pixel, and applying a second precharge voltage to the second pixel. And applying a second precharge voltage, wherein the first pixel and the second pixel are alternately arranged adjacent to each other in a row direction. In this way, distortion of the common voltage due to coupling at the time of rising or falling of the data voltage can be prevented.

Coupling, LCD, Signal Controller, Common Voltage, Distortion, Flicker, Crosstalk

Description

Driving method of liquid crystal display {DRIVING METHOD OF LIQUID CRYSTAL DISPLAY}

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of one pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a waveform diagram according to an embodiment of the present invention.

The present invention relates to a method of driving a liquid crystal display.

A typical liquid crystal display (LCD) includes two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors (TFTs) to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the display panel and receives a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor, and the liquid crystal capacitor becomes a basic unit that forms a pixel together with a switching element connected thereto.                         

In such a liquid crystal display, a voltage is applied to two electrodes to form an electric field in the liquid crystal layer, and the intensity of the electric field is adjusted to control the transmittance of light passing through the liquid crystal layer to obtain a desired image. At this time, in order to prevent deterioration caused by the application of an electric field in one direction to the liquid crystal layer for a long time, the polarity of the data voltage with respect to the common voltage is inverted frame by frame, row, or dot.

Meanwhile, in order to increase the charging time of the liquid crystal, a precharge signal TP for precharging a predetermined voltage is applied immediately before applying the data voltage to the pixel.

At this time, distortion of the common voltage due to coupling during a specific inversion driving occurs. For example, during 1 + 2 dot inversion driving, 1 dot inversion is performed in the first pixel row, and 2x1 dot inversion is performed in the next pixel row. Therefore, normal dot inversion is performed in units of two rows. At this time, the precharge signal is applied when the data voltage transitions from the negative black gray voltage to the negative white gray voltage, or when the data voltage transitions from the positive white gray voltage to the positive black gray voltage. It causes the rise or fall of the common voltage. This in turn results in non-uniformity of the entire screen, causing crosstalk or flicker.

Accordingly, an object of the present invention is to provide a method of driving a liquid crystal display device capable of preventing distortion of a common voltage.

According to an embodiment of the present invention for achieving the above technical problem, a plurality of pixels arranged in a matrix form, a signal controller for providing a control signal, a data driver for supplying a data voltage in accordance with the control signal, the data voltage A driving method of a liquid crystal display device including a plurality of data lines transferred to a pixel includes applying a first precharge voltage to a first pixel, and applying a second precharge voltage to a second pixel. Here, the first pixel and the second pixel may be alternately arranged adjacent to each other in the row direction, wherein the first pixel includes two pixels neighboring in the row direction, and the second pixel is arranged in the first pixel. It may include two pixels neighboring in the direction. In this case, the second precharge voltage is applied at a predetermined interval from the first precharge voltage, and the predetermined interval is preferably 150 to 250 ns.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right on" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A method of driving a liquid crystal display according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of a pixel of a liquid crystal display device according to an embodiment of the present invention.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, a data driver 500, and a data driver The gray voltage generator 800 connected to the signal generator 500 and a signal controller 600 for controlling the gray voltage generator 800 are included.

The liquid crystal panel assembly 300 includes a plurality of display signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels connected to the plurality of display signal lines G ₁ -G _n , D ₁ -D _m , and arranged in a substantially matrix form. .

The display signal lines G ₁ -G _n and D ₁ -D _m are a plurality of gate lines G ₁ -G _n for transmitting a gate signal (also called a “scan signal”) and a data signal line or data for transmitting a data signal. Line D ₁ -D _m . The gate lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _m extend substantially in the column direction and are substantially parallel to each other.

Each pixel includes a switching element Q connected to a display signal line G ₁ -G _n , D ₁ -D _m , and a liquid crystal capacitor C _LC and a storage capacitor C _ST connected thereto. It includes. The holding capacitor C _ST can be omitted as necessary.

The switching element Q is provided on the lower panel 100, and the control terminal and the input terminal are connected to the gate line G ₁ -G _n and the data line D ₁ -D _m, respectively. The output terminal is connected to the liquid crystal capacitor C _LC and the storage capacitor C _ST .

The liquid crystal capacitor C _LC has two terminals, the pixel electrode 190 of the lower panel 100 and the common electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 190 and 270. It functions as a dielectric. The pixel electrode 190 is connected to the switching element Q, and the common electrode 270 is formed on the front surface of the upper panel 200 and receives a common voltage V _com . Unlike in FIG. 2, the common electrode 270 may be provided in the lower panel 100. In this case, both electrodes 190 and 270 may be linear or rod-shaped.

The storage capacitor C _ST is formed by overlapping a separate signal line (not shown) and the pixel electrode 190 provided on the lower panel 100, and a predetermined voltage such as a common voltage V _com is applied to the separate signal line. Is approved. However, the storage capacitor C _ST may be formed such that the pixel electrode 190 overlaps the front end gate line directly above the insulator.

Meanwhile, in order to implement color display, each pixel must display color, which is possible by providing a red, green, or blue color filter 230 in a region corresponding to the pixel electrode 190. In FIG. 2, the color filter 230 is formed in a corresponding region of the upper panel 200. Alternatively, the color filter 230 may be formed above or below the pixel electrode 190 of the lower panel 100.

A polarizer (not shown) for polarizing light is attached to an outer surface of at least one of the two display panels 100 and 200 of the liquid crystal panel assembly 300.

The gray voltage generator 800 generates two sets of gray voltages related to the transmittance of the pixel. One of the two sets has a positive value for the common voltage (V _com ) and the other set has a negative value.

The gate driver 400 is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300 to receive a gate signal formed by a combination of a gate on voltage V _on and a gate off voltage V _off from the outside. It is applied to the gate lines G ₁ -G _n .

The data driver 500 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300 to select the gray voltage from the gray voltage generator 800 and apply the gray voltage to the pixel as a data signal. It consists of a circuit.

The signal controller 600 generates control signals for controlling operations of the gate driver 400 and the data driver 500, and provides the corresponding control signals to the gate driver 400 and the data driver 500.

Next, the display operation of the liquid crystal display will be described in more detail.                     

The signal controller 600 inputs an input control signal for controlling the RGB image signals R, G, and B and their display from an external graphic controller (not shown), for example, a vertical sync signal V _sync and a horizontal sync signal. (H _sync ), a main clock (MCLK), a data enable signal (DE) is provided. The signal controller 600 generates a gate control signal CONT1 and a data control signal CONT2 based on the input control signal, and adjusts the image signals R, G, and B to match the operating conditions of the liquid crystal panel assembly 300. After appropriately processing, the gate control signal CONT1 is sent to the gate driver 400, and the data control signal CONT2 and the processed image signals R ', G', and B 'are sent to the data driver 500.

The gate control signal CONT1 includes a vertical synchronization start signal STV indicating the start of output of the gate on pulse (gate on voltage section), a gate clock signal CPV for controlling the output timing of the gate on pulse, and a gate on pulse. An output enable signal OE or the like that defines a width.

The data control signal CONT2 is a load for applying a corresponding data voltage to the horizontal synchronization start signal STH indicating the start of input of the image data R ', G', and B 'and the data lines D ₁ -D _m . Signal LOAD, inverted signal RVS and data that inverts the polarity of the data voltage with respect to common voltage V _com (hereinafter referred to as " polarity of data voltage " by reducing " polarity of data voltage with respect to common voltage "). Clock signal HCLK and the like.

The data driver 500 sequentially receives image data R ′, G ′, and B ′ corresponding to one row of pixels according to the data control signal CONT2 from the signal controller 600, and generates a gray voltage generator ( The image data R ', G', B 'is converted into the corresponding data voltage by selecting the gray voltage corresponding to each of the image data R', G ', and B' among the gray voltages from the 800.

The gate driver 400 applies the gate-on voltage V _on to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600, thereby applying the gate lines G ₁ -G _n. Turn on the switching element (Q) connected to.

The gate-on voltage V _on is applied to one gate line G ₁ -G _n so that a row of switching elements Q connected thereto is turned on (this period is "1H" or "1 horizontal period). (horizontal period) "and equal to one period of the horizontal sync signal Hsync, the data enable signal DE, and the gate clock CPV], and the data driver 500 converts each data voltage to a corresponding data line D. ₁ -D _m ). The data voltage supplied to the data lines D ₁ -D _m is applied to the corresponding pixel through the turned-on switching element Q.

The liquid crystal molecules change their arrangement according to the electric field generated by the pixel electrode 190 and the common electrode 270, and thus the polarization of light passing through the liquid crystal layer 3 changes. The change in polarization is represented by a change in transmittance of light by a polarizer (not shown) attached to the display panels 100 and 200.

In this manner, the gate-on voltages V _{on are} sequentially applied to all the gate lines G ₁ -G _n during one frame to apply data voltages to all the pixels. When one frame is finished, the next frame is started and the state of the inversion signal RVS applied to the data driver 500 is controlled so that the polarity of the data voltage applied to each pixel is opposite to the polarity of the previous frame ("frame"reversal"). In this case, the polarity of the data voltage flowing through one data line may be changed (“line inversion”) within one frame or the polarity of the data voltage applied to one pixel row may be different according to the characteristics of the inversion signal RVS ( "Dot reversal").

Meanwhile, the liquid crystal display according to the exemplary embodiment of the present invention performs 1 + 2 dot inversion and drives the precharge signal at predetermined intervals, which will be described in detail with reference to FIG. 3.

3 is a waveform diagram according to an embodiment of the present invention.

3 illustrates a portion D ₁ -D ₄ of the data lines D ₁ -D _m and data voltages and precharge signals TP1 and TP2 applied thereto, and the dotted lines in the horizontal direction represent the common voltage V _com. ).

As shown, in the case of the first and third data lines D ₁ and D ₃ , data voltages are applied in the order of +,-,-, +, +, .. polarities, and the second and fourth data. In the case of the lines D ₂ and D ₄ , the data voltages are applied in the order of-, +, +,-,-, ... polarity. Of course, the data voltage applied from the data driver 500 is applied through each channel connected to the data driver IC forming the data driver 500. However, in the present embodiment, the data voltage is applied through the data line for convenience of description.

In the driving method of the liquid crystal display according to the exemplary embodiment of the present invention, the precharge signal is divided into an even line and an odd line. That is, the first and second data lines D ₁ and D ₂ are divided into odd lines D _odd , and the third and fourth data lines D3 and D4 are divided into even lines D _even . The other data lines (not shown) are also arranged in alternating odd and even lines in pairs of two.

The precharge signal TP1 applied to the _odd line D _odd and the precharge signal TP2 applied to the even line D _even are applied at predetermined time intervals, which are indicated by arrows. In general, the time required to apply the precharge signal is 300 to 500 ns, so it is preferable to divide and apply the precharge signal. That is, 150 to 250 ns may be applied after the first precharge signal is applied.

In addition, this means a time interval such that there is no influence of coupling by charging. In this way, the influence of the coupling due to the precharge signal applied when the data voltage falls or rises in each pixel row can be minimized to prevent distortion of the common voltage.

The precharge signals TP1 and TP2 may be applied through the signal controller 600, or may use a separate delay circuit (not shown). When the precharge signal is applied through the signal controller 600, the signal can be divided into two signals having a predetermined time interval from the beginning. In the case of using a delay circuit, one precharge signal is first applied to the odd lines, The precharge signal output from the delay circuit may be applied to even lines.

In this way, the data lines D ₁ -D _m are divided into even lines (D _even ) and odd lines (D _odd ) to apply the precharge signals TP1 and TP2 to thereby eliminate distortion of the common voltage V _com . It can prevent.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (5)

A plurality of pixels arranged in a matrix form, a signal controller providing a control signal, a data driver supplying a data voltage according to the control signal, a plurality of data lines transferring the data voltage to the pixel and extending in a column direction, and A driving method of a liquid crystal display device including a plurality of gate lines extending in a row direction and transmitting a gate signal, The control signal includes a precharge signal for charging a predetermined voltage to the pixel in advance. Each of the plurality of data lines includes a first data line set and a second data line set each including at least one data line; The plurality of gate lines includes a first gate line, Applying a first precharge voltage to the pixel connected to the first data line set and the first gate line, and Applying a second precharge voltage to the pixel connected to the second data line set and the first gate line; Including, The second precharge voltage is applied at a predetermined interval from the first precharge voltage. While the first precharge voltage is applied to the pixel connected to the first data line set and the first gate line, the first precharge voltage is applied to the pixel connected to the second data line and the first gate line. Unauthorized Driving method of liquid crystal display device. In claim 1, And the first data line set and the second data line set are alternately arranged in a row direction. In claim 2, When the plurality of data lines are paired in turn, the first data line set includes an odd-numbered data line pair, and the second data line set includes an even-numbered data line pair. Method of driving the display device. 4. The method of claim 3, And the predetermined interval between which the second precharge voltage and the first precharge voltage are applied is shorter than one horizontal period. 4. The method of claim 3, The predetermined interval is 150 to 250ns driving method of the liquid crystal display device.

Images